Treatment of Hodgkin disease (HD) in ataxia telangiectasia (AT) patients is hampered by hypersensitivity to radiation and chemotherapy. Most patients die, due to toxicity or, rarely, to progressive disease. The authors report on a 9-year-old girl with stage IIA HD and AT. She was treated with a tailored combined modality approach. No unacceptable toxicity was found, but the girl died of a relapse outside their radiation field. In comparison with fibroblasts of non-AT patients, the fibroblasts of the patient were 3 times as sensitive for radiotherapy but just 1.2 times as sensitive for doxorubicin. A good correlation was shown between in vitro radio- and chemosensitivity testing and the observed clinical toxicity. The authors suggest, therefore, treating AT patients as much as possible according to standard protocols by adjusting the radiotherapy delivery and the chemotherapy regimen to individual doses derived from in vitro radio- and chemosensitivity testing.